There are also several scientific papers and journal papers available that elaborate about the open source BIMserver.
An arbitrary listof papers can be found on this page. There are many other papers that mention BIMserver or open source BIM projects. A good source to find them is Google Scholar.

2010, Beetz, de Laat, van Berlo, van den Helm; “Towards an Open Building Information Model Server Report on the progress of an open IFC framework”. Published in proceedings DDSS conference Eindhoven (pdf).

2012, W. Mazairac & J. Beetz; “Towards a Framework for a Domain Specific Open Query Language for Building Information Models”. Published at International Workshop Intelligent Computing in Engineering, July 4-6, 2012 in Herrsching (Munich) Germany (pdf).

2012, Glawischnig, Stefan, et al. “Recent advances in the development of MOST: an open-source, vendor and technology independent toolkit for building monitoring, data preprocessing and visualization.” (link).